An unrepentant Shane Flanagan has refused to back down over his criticisms of the referees after Cronulla's shock exit from the finals series, describing comments from NRL chief executive Todd Greenberg that he had hurt the game as "ridiculous."

Flanagan has been slapped with a $30,000 fine after he described the performance of the referees as "disgraceful" after the Sharks loss to North Queensland on Sunday, with the club still debating whether to contest the breach notice.

Manly coach Trent Barrett was also hit with a $20,000 fine for criticising the referees after the loss to Penrith on Saturday night, with the Sea Eagles also considering their right to appeal.

The attacks prompted Greenberg to draw a line in the sand and tell coaches and clubs to grow up over the increasing attacks on referees, claiming he was sick of the culture that saw match officials being blamed for a loss.